Hard magnetic bias configuration for GMR

Abstract

A longitudinal bias structure for use in a GMR device is described. Improved magnetic properties of the bias structure are achieved by inserting an extra layer between the seed layer and the bias layer. This layer has lattice constants that are intermediate between those of the seed and bias layers thereby improving the crystallinity of the latter. Specifically, a layer of chromium-cobalt-tantalum is inserted between a seed layer of chromium, or chromium-titanium, and a hard magnetic (bias) layer of cobalt-chromium-platinum or cobalt-platinum. About 20 Angstroms is optimum for the thickness of this layer. Data is presented showing that significant improvements in coercivity and hysteresis loop squareness are obtained.

What is claimed is:  
     
       1. A longitudinal bias structure for use in a GMR based magnetic read head, comprising: 
       a substrate;  
       on said substrate a seed layer of chromium;  
       on the chromium layer a buffer layer that is an alloy of cobalt, chromium, and tantalum, said buffer layer having a thickness between about 10 and 100 Angstroms;  
       a layer of tantalum, between about 10 and 100 Angstroms thick, between the substrate and the seed layer; and  
       on the buffer layer, a magnetically hard layer that is an alloy of cobalt, chromium and platinum.  
     
     
       2. The structure described in  claim 1  wherein the buffer layer is between about 70 and 93 atomic percent cobalt, between about 5 and 25 atomic percent chromium, and between about 2 and 10 atomic percent tantalum. 
     
     
       3. The structure described in  claim 1  wherein the chromium layer has a thickness between about 20 and 150 Angstroms. 
     
     
       4. The structure described in  claim 1  wherein the magnetically hard layer has a thickness between about 100 and 600 Angstroms. 
     
     
       5. The structure described in  claim 1  wherein the magnetically hard layer is between about 50 and 93 atomic percent cobalt, between about 5 and 25 atomic percent chromium, and between about 2 and 50 atomic percent platinum. 
     
     
       6. A longitudinal bias structure for use in a GMR based magnetic read head, comprising: 
       a substrate;  
       on said substrate a seed layer that is an alloy of chromium and titanium;  
       on the chromium layer a buffer layer that is an alloy of cobalt, chromium, and tantalum, said buffer layer having a thickness between about 10 and 100 Angstroms;  
       a layer of tantalum, between about 10 and 100 Angstroms thick, between the substrate and the seed layer; and  
       on the buffer layer, a magnetically hard layer that is an alloy of cobalt, chromium and platinum.  
     
     
       7. The structure described in  claim 6  wherein the buffer layer is between about 70 and 93 atomic percent cobalt, between about 5 and 25 atomic percent chromium, and between about 2 and 10 atomic percent tantalum. 
     
     
       8. The structure described in  claim 6  wherein the seed layer has a thickness between about 20 and 150 Angstroms. 
     
     
       9. The structure described in  claim 6  wherein the magnetically hard layer has a thickness between about 100 and 600 Angstroms. 
     
     
       10. The structure described in  claim 6  wherein the magnetically hard layer is between about 50 and 93 atomic percent cobalt, between about 5 and 25 atomic percent chromium, and between about 2 and 10 atomic percent platinum. 
     
     
       11. The structure described in  claim 6  wherein the seed layer is between about 80 and 95 atomic percent chromium and between about 5 and 20 atomic percent titanium. 
     
     
       12. A process for forming a longitudinal bias structure for use in a GMR based magnetic read head, comprising: 
       on a substrate, depositing, to a thickness between about 20 and 150 Angstroms, a seed layer that comprises chromium;  
       on the seed layer, depositing a buffer layer that is between about 70 and 93 atomic percent cobalt, between about 5 and 25 atomic percent chromium, and between about 2 and 10 atomic percent tantalum to a thickness between about 10 and 100 Angstroms; and  
       on the buffer layer, depositing, to a thickness between about 100 and 600 Angstroms, a magnetically hard layer that is between about 50 and 93 atomic percent cobalt, between about 5 and 25 atomic percent chromium, and between about 2 and 50 atomic percent platinum.  
     
     
       13. The process described in  claim 12  further comprising depositing a layer of tantalum, between about 10 and 100 Angstroms thick, between the substrate and the seed layer. 
     
     
       14. The process described in  claim 12  wherein the seed layer further comprises between about 80 and 95 atomic percent chromium and between about 5 and 20 atomic percent titanium. 
     
     
       15. A process for forming a longitudinal bias structure for use in a GMR based magnetic read head, comprising: 
       on a substrate, depositing, to a thickness between about 20 and 150 Angstroms, a seed layer that comprises chromium;  
       on the seed layer, depositing a buffer layer that is between about 70 and 93 atomic percent cobalt, between about 5 and 25 atomic percent chromium, and between about 2 and 10 atomic percent tantalum to a thickness between about 10 and 100 Angstroms; and  
       on the buffer layer, depositing, to a thickness between about 100 and 600 Angstroms, a magnetically hard layer that is between about 50 and 95 atomic percent cobalt and between about 5 and 50 atomic percent platinum.  
     
     
       16. The process described in  claim 15  further comprising depositing a layer of tantalum, between about 10 and 100 Angstroms thick, between the substrate and the seed layer. 
     
     
       17. The process described in  claim 15  wherein the seed layer further comprises between about 80 and 95 atomic percent chromium and between about 5 and 20 atomic percent titanium.